1. Field of the Invention
The present invention relates to an automatic steering apparatus for a vehicle, to automatically park the vehicle without a driver's steering operation.
2. Description of the Prior Art
An automatic steering apparatus is known which utilizes an actuator of a known electrically powered steering apparatus, and is adapted to automatically carry out the back parking and longitudinal parking of a vehicle by controlling the actuator on the basis of the relation between the distance of movement of the vehicle and the steering angle which are stored in advance. Such an apparatus is disclosed in Japanese Patent Application Laid-Open Nos. 3-74256 and 4-55168.
There is a technique of detecting the traveling distance of a vehicle on the basis of the number of rotations of a wheel by using a sensor for sensing the teeth formed at the outer circumferential portion of a disc rotating with the wheel, and determining the number of rotations of the wheel on the basis of pulses obtained by sensing the teeth on the rotating disc. In such a technique, the rotational direction of the wheel (i.e. the traveling direction of the vehicle) cannot be determined. Accordingly, for example, when an automatic parking control is carried out while moving the vehicle forward with the gear selecting lever set in "D" range, and the vehicle moves backward due to the inclination of the road surface, the control unit erroneously judges that the vehicle travels forward, and carries out automatic steering operation since the traveling direction of the vehicle cannot be determined by the conventional technique. Consequently, the locus of movement of the vehicle deviates greatly from a predetermined path.